chore: update Go version and dependencies for builds

- Update Go version from `1.20` to `1.21` in go.mod, .github/workflows/build.yml, and .github/workflows/lint.yml

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        goVer: ["1.20"]
+        goVer: ["1.21"]
 
     steps:
     - name: Set up Go ${{ matrix.goVer }}

.github/workflows/lint.yml

@@ -13,7 +13,7 @@ jobs:
       - name: Set Golang
         uses: actions/setup-go@v3
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - name: Checkout code
         uses: actions/checkout@v3
       - name: Lint

.github/workflows/release.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Use Golang
         uses: actions/setup-go@v3
         with:
-          go-version: "1.20"
+          go-version: "1.21"
 
       - name: Build with xgo
         uses: crazy-max/ghaction-xgo@v2